Custom URL for Shared Box Link
Externally shared Box links have a mandatory expiration date, and the only way to ‘extend’ the date is to delete the current shared link and make a new one. However, this will create a new randomized URL as well, so the new URL would have to be sent out to any external entities who previously had access. Creating a custom URL for the shared Box link can be a workaround for this, as the URL will remain the same after deleting/re-sharing the folder/item.
Navigate to the folder/file to be shared
Click on Share in the top right
Go to the shared link settings
Click Link Settings > Non-private custom URL
Check the Non-private Custom URL box
Fill out the name you want the link to have
Click Save in the bottom right
When you need to delete a shared link and recreate it, follow the same steps above with the same name and that should allow the original link to be accessible with an extended expiration date.